I could see Stephanie being Jan. Even with that "nail in the coffin" cherokee is so adamant about. Kevin Feige may have said the following:

but what does that really mean? As stated above, "any of the other Avengers" only includes Hulk, Thor, Cap, BW and Hawkeye at this point. So that rules them out. And Nick Fury is out. But about those "world-blending conceits" ... ?
IM2 blended Cap, IM and Thor (alluding to Tesseract, Caps shield, New Mexico)
Thor blended TIH and IM (with Coulson and Selvigs lines about Banner)
CA:TFA blended Cap, IM and Thor (with Norway, Howard Stark etc.)
TIH mentioned Stark-tech and cameo'd RDJ, not to mention the Super Soldier program.

Thing is, Janet and Hank... don't have a world to blend yet. Their solo film doesnt come until 2015. They aren't Avengers, they aren't a part of SHIELD (so far as we know) and Jan could very well be introduced as an Iron Man character until further notice.

At that, perhaps Hank will be introduced as a Captain America or Thor character long before he gets his solo film.

I'm not really concerned with the world blending seen in IM2. Black Widow fit pretty well in my opinion and her original first appearance was in an Iron Man comic anyway. And in the same vein she may someday get her own solo movie.

I agree with everything here. Janet and Stark have a history(even though it came after her and Pym were together) but still that's easy to rectify so having her appear in IM3 is easy enough.

And Dent maybe they want to keep her character a secret until the movie comes out.